1. Field of the Invention
The present invention relates to the preparation process of high cementitious cement clinker, more specifically, it relates to secondary synthetic method of calcium sulphoaluminate in Portland cement clinker.
2. Description of the Related Art
The key issue in the preparation of Portland cement clinker containing C4A3 S (Ye'elimite) mineral is the problem of coexistence of C4A3 S and Alite, wherein C4A3 S mineral decomposes largely at 1350° C., while the formation of Alite in clinker starts at 1450° C. Therefore, from thermodynamics point of view, C4A3 S and Alite cannot co-exist in the same system. At present, Portland cement clinker containing C4A3 S mineral is mainly prepared by doping fluorite and gypsum to Portland cement raw meal, which then is calcined at 1300˜1400° C.
However, at present, most of cement is prepared via dry calcination in China, where the calcination temperature is around 1450° C. As a result, most of the C4A3 S formed in the cement clinker has been decomposed, leaving only a small amount of C4A3 S in cement clinker. This results in a deficiency of certain properties (such as initial strength) of Portland cement containing C4A3 S mineral. Therefore, methods for preparation of Portland cement clinker containing C4A3 S have not been industrialized in China and most of cement enterprises still produce traditional Portland cement clinker in pre-calcining kiln.